Clinical Outcomes of Patients With Lateral Femoral Cutaneous Nerve Injury After Direct Anterior Total Hip Arthroplasty.

BACKGROUND:
Direct anterior total hip arthroplasty (THA) is an increasingly utilized and patient-requested approach for arthroplasty carrying a unique set of complications. Injury to the lateral femoral cutaneous nerve (LFCN) can have a wide range of clinical symptoms ranging from hypesthesia to painful paresthesia. Long-term effects of this injury have not been well studied. We describe duration and severity of these symptoms and correlate their relationship with hip functional scores.

METHODS:
Between January 2009 and January 2016, 1665 patients with 1871 hips who underwent direct anterior THA by a single surgeon were surveyed for reported outcomes including Douleur Neuropathique 4-Interview (DN4-I), Hip Disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS, JR), and Patient-Reported Outcomes Measurement Information System Short Form Global Health Assessment. The DN4-I was considered positive if 3 (or more) of 7 neuropathic pain symptoms were affirmed at present in the distribution of the LFCN of the affected leg.

RESULTS:
Six hundred eighty patients accounting for 778 hips completed the survey. Overall, 16% of responders had positive DN4-I scores for continued neuropathic symptoms with a mean time since surgery of 3.9 years at assessment. Twenty-four percent of those responding within 2 years of surgery had positive scores compared with 15% from 2 to 4 years, 14% from 4 to 6 years, and 11% positive from 6 to 8 years after surgery. Of those with positive DN4-I scores, the most commonly affirmed neuropathic symptom was "numbness", reported in 37% of patients. The overall average interval HOOS, JR score was 89.8. There were no differences in HOOS, JR or Patient-Reported Outcomes Measurement Information System scores for patients further out from surgery.

CONCLUSION:
The most commonly experienced neuropathic symptom in the distribution of the LFCN following direct anterior THA is "numbness" that occurred in 37% of patients with a positive DN4-I score. Neuropathic symptoms improved in patients further out from surgery with pain reported in 11% of patients from 6 to 8 years postoperatively. Neuropathic symptoms significantly improve with time and appear to be independent of hip function scores.